1. The Field of the Invention
The present invention is directed generally to a modular plural component spray system. More specifically, the present invention is directed to a modular plural component spray system where each component is transported to a spray gun without requiring a transfer pump.
2. Background Art
Spray foam has been in use for about 50 years. Polyurea/urethane fast-set elastomeric coatings have been in use for about 20 years. For coatings and the like, two-part self-setting compounds may be mixed in a desired ratio and applied to the target surface or part. Compounds react quickly, yet the foam or coatings are sprayed at typically from 1-3 Gallons Per Minute (GPM). In most applications, the components mix within the plural component spray gun just before exiting to the target surface.
One of the biggest complaints about current spray foam equipment is that the equipment is difficult to learn to use, and is prone to failure due to too many electronics and related equipment that is not easy for the layman contractor/sprayer to troubleshoot and fix. Down time of spray foam equipment is costly, and can prevent timely completion of projects. Moreover, replacement parts are expensive and may require significant lead times to acquire.
Another problem in the industry is that most modern proportional spray foam systems do not provide the desired ratio of components, for example a 1:1 by volume ratio for the spray components. Typically, current systems therefore deliver a mixture that does not have the proper stoichiometry or the best physical properties of the components. Another disadvantage of prior art systems is that they frequently heat the components while they are still in the drum, which can cause problems. For example, heating the components prior to pumping will lower the viscosities and can cause striation, resulting in premature expansion of the B resin foam, which is then impractical to pump. The lowered viscosity may also cause leaking at the pump seals.
Yet another disadvantage of prior art systems is the use of pneumatic drive systems for the pumps, requiring a large volume of pressurized air. Suitable pneumatic systems are noisy, dirty and require larger air compressors.
Particular illustrative examples of applications for spray foam systems include, without limitation, (i) building insulation; (ii) roofing insulation; (iii) marine craft floatation material and motor vehicle crash space volumes; (iv) pipe insulation; (v) foam molding of parts, including for example wave boards; (vi) insulation for commercial freezers and refrigeration systems; (vii) commercial specialty building domes that are otherwise difficult to insulate; (viii) concrete leveling; (ix) prosthetic bones for training; (x) flotation items, including for example docks; (xi) props for type entertainment centers, for example fake rocks for resorts; (xii) military tent insulation; and the like.
Particular illustrative example of applications for polyurea/urethane elastomeric coatings include, without limitation: (i) floors; (ii) pickup truck bed liners; (iii) secondary containment, for example sewage clarifiers; (iv) military bullet proofing and bomb-fragment protection; (v) roof coatings; (vi) injection molding; and the like.
Both the spray foam industry and the polyurea/urethane elastomeric coatings industry use the same or similar equipment, and are collectively referred to herein as “spray foam equipment,” “spray system” or similar phraseology. Typically, polyurea/urethane elastomeric coatings simply use higher heat and pressure.
U.S. Pat. Pub. No. 2012/0282121 of Kieffer et. al. (hereinafter Kieffer) discloses a plural component pump system for delivering plural liquid components at a selected ratio. The pump system includes a first brushless DC motor configured to drive a first pump that pumps a first liquid component to an output and a second brushless DC motor configured to drive a second pump that pumps a second liquid component to the output. The pump system includes a first controller configured to control the first motor and a second controller configured to control the second motor. The pump system also includes a communication interface between the first controller and the second controller. The first controller is configured to send a signal to the second controller using the communication interface and the second controller is configured to control the second motor based on the signal to deliver the first and second liquid components to the output at the selected ratio.
Each of Kieffer's electric motor cam driven piston pumps is driven by an electric motor of the on-off type. When such a piston pump receives a demand for a component, the motor coupled to the pump is turned on, causing a short cam action drive of the piston pump. Such a pump includes a very short stroke length, e.g., a GRACO® reactor having a 1¼″ cam to give only a 2.5″ full stroke length. Kieffer's pump has limited draft and can only siphon a very short distance with the pump (602 or 604 of Kieffer) mounted directly atop a drum (608 or 610 of Kieffer). As each of Kieffer's pumps is an on-off type pump capable of operating at fixed speeds only, in order to control Kieffer's pump speed to result in a different flow rate, Kieffer's pump would need to be stopped and started numerous times, causing undesirable pulsations revealed at a spray gun receiving the component from the pump.
Another characteristic of Kieffer's electronic motor cam driven piston pump has to deal with its output. The piston of such a pump is smaller and therefore causes much lower output per unit time. Upon examination of a pump chart documenting a volume flow to pressure, it shall be apparent that the flow pressure falls off quickly in relation to the volume of liquid moved as shown in FIG. 1. Kieffer's motors are small and do not have the capabilities to deliver larger volumes of fluids. Kieffer's pump is only capable of from about 0.5 to 0.7 GPM, a very low output compared to a hydraulic reciprocating piston pumps at about 2.5 GPM. In the plural component delivery industry, a pump used for delivering a component needs to be three times the volume output of the gun in order to deliver the volume and pressure up to about 3,500 Pounds Per Square Inch (psi). Further, most conventional spray guns used for the foam and coating industry include orifice sizes of from about 1 to 2.5 GPM. Kieffer's pump is incapable of providing sufficient flow for orifices with such sizes.
Yet other types of pumps have been attempted but all fail to satisfy consumer needs as the materials being pumped (e.g., isocyanate, etc.) in the coating industry have great tendencies to cause clogging of moving parts of the pumps. Among pumps which have been attempted but found to be undesirable, are positive displacement pumps such as axial piston and gear pumps.
Other undesirable setups of spray systems include a flow line having multiple pumps which not only add complexity to the setups as compared to a flow line with only one pump, but also causes the operation of a first pump to interfere with the operation of a second pump in the same flow line. The multi-pump per flow line setups such as those disclosed in the following website represent conventional plural component spray systems: http://www.sprayworksequipment.com/pages/how_a_spray_foam_machine_works.html There arises a need for a modular plural component spray system which is capable of meeting the volumetric flowrate of plural components of at least from about 3 to about 4 GPM and can be operated without pulsations and other negative flow effects.